Due to the rise of the Internet, cellular phones, virtual private networks, and the like, there is a growing need for faster and faster communication systems to handle the tremendous increase in information being transmitted. One of the areas where this demand is the greatest is in the area of optical communications.
Optical transmission systems in the 10 Gb/s range are already becoming commonplace; systems operating at 40 Gb/s (and higher) are now in development. However, the production of high speed transmitters and receivers in the 40 Gb/s range has been greatly hampered due to limitations in the materials used to create the wiring boards on which these components sit.
Traditionally, optical components for these high speed systems have been integrated on a substrate such as aluminum oxide (Al2O3), wherein active alignment must be used to align the optical elements on the wire board. As an alternative, a combination of a silicon optical bench (SiOB) for the optical devices, and an Al2O3-based high speed electrical circuit board has been used, incorporating ribbon bonding, flip-chip soldering and/or flex cables to interconnect the two components.
However, these systems of the prior art have significant disadvantages. The active optical alignment required by conventional Al2O3 wire boards is expensive and cost prohibitive. The active alignment of optical fibers to laser diodes or photodetectors is a time consuming process, which makes automated production extremely difficult. Moreover, the facilities needed to manufacture these systems require a considerable investment with a reasonably large volume production.
As a result, a silicon optical bench (SiOB) is preferable as a substrate for the optical elements. The use of silicon as a substrate allows for the passive alignment of the laser/photodiode (i.e., “active optical device”) to the optical fiber, such as through the use of arrays of etched V-grooves in the silicon, reducing production costs. For example, a wafer-scale package process may be used for volume production of hybrid integrated optical components, by using the passive alignment of the precisely cleaved laser diode and semiconductor waveguide onto a micro-machined silicon optical bench.
Alternatively, a batch transporting technique can be employed, in which a micro-machined silicon guiding plate may be used as a processing unit through the entire manufacturing procedure from die bonding to hermetic sealing. Such a system is disclosed in Jan-Jun Koh, et al., On-Wafer Process for Mass Production of Hybridly Integrated Optical Components Using Passive Alignment on Silicon Motherboard, the 51st Electronic Components and Technology Conference, Lake Buena Vista, Fla., May 29-Jun. 1, 2001, page 6.
Unfortunately, however, conventional silicon-based wire boards have not been considered as a good choice for the electrical circuit components in high speed optical wire boards, primarily due to excessive RF insertion loss in the silicon.
Accordingly, a system is needed which provides a stable and accurate passive alignment of the optical components on the optical sub-assembly of a high speed optical wire board, while simultaneously achieving satisfactory RF-performance of the electrical circuit mounted on the same substrate.